Compressional wave translating device



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April 5,14

A- c. KELLER v COMPRESSIONAL WAVE TRANSLATING DEVICE Filed Dec. 31, 194.2

'INI/ENTOR A. C. KELLER av (MM 6. 7M

ATTORNEY Patented Apr. 5, 1949 UNITED STATES PATENT OFFICE COMPRESSIONAL WAVE TRAN SLATING DEVICE Arthur 0. Keller, Bronxville, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 31, 1942, Serial No. 470,808

' the construction of crystal array type compressional wave translating devices.

' In one illustrative embodiment of this invention, a supersonic compressional Wave device, suitable for use both as a transmitter and a receiver in submarine signaling equipment, comprises a linear array of piezoelectric crystals electrically in parallel, the crystals being in the form. of rectangular blocks, and supports for mounting the crystals.

2 prises a fluid-tight housing Ill highly transparent to supersonic wave energy and having a filling of a viscous fluid, such as castor oil, having substantially the same impedance to transmission of wave In accordance with one feature of this invention, the blocks constitutin the array are divided into 'twoor more groups, the blocks in the several groups being, in interposed relation and the blocks in each group extending at an angle to the others. In one construction, the crystal blocks are mounted in superposed centrally aligned relation with adjacent blocks extending at right angles to one another so that the array comprises two groups of alternately arranged crystal blocks in quadrature.

In accordance with another feature of this invention, the crystal blocks are mounted in stacked relation and are held in position laterally by guiding means engaging the blocks- The invention and the above-noted and other features thereof will be understood more clearly and fully from the followin detailed description with reference to the accompanying drawingin which:

Fig. 1 is an elevationalview in perspective of a submarine signaling device illustrative of 7 one embodiment of this invention, the housing for the crystal array being shown in phantom;

Fig 2 is a cross-sectional view of the device il- I lustrated'in Fig. 1;

Fig. 3 is a detail perspective view of one of the crystal blocks and the electrodes and leading-in conductors therefor; and

Fig. 4 is a cross-sectional view of a modification of the device illustrated in Figs. 1 and 2.

Referring now to the drawing, the submarine signaling device illustrated in Figs. 1 to 3 comenergy as sea water. Mounted within the housing is a supporting frame including end members [I and I2, for example discs of insulating material, and a plurality of insulating guide for positioning posts l3, for example four posts arranged at thecorners of a square as shown in Fig. 2, secured to the end discs I l and I2.

Positioned by and between the guide posts l3 -are a pluralit of similar piezoelectric crystals l4,

which may e advantageously -degree Y-cut rectangular Rochelle crystal blocks. Each block is of a length substantially equal to one-half wave-length of the frequency at which the device is to be operated, if single frequency operation is intended, or to one-half wave-length of the highest frequency to be translated if the device is intended for operation within a predetermined band of frequencies, and is of such thickness that the center tocenter spacing of adjacent blocks is less than one-half wave-length of the intended operating frequency or of the highest frequency in the band to be translated.

As shown in Fig. 1, advantageously, for reasons to be pointed. out hereinafter, the two crystal blocks at each end of the array may be of twice the thickness of the remaining blocks. The several blocks are centrally aligned and engaged and positioned laterally by the guide posts l3. Adjacent crystal blocks are arranged at right angles to one another, thus providing an array composed of two groups of crystals in space quadrature.

As shown clearly in Fig, 3, each of the crystals I4 is provided on opposite faces, the upper and lower faces in Fig. 1, with electrodes l5 which may .be, for example, coatings of gold evaporated onto each'of the electrodes '15. The foil strips I6 ex-' .tend into slots in two'of'the guide posts l3, the

conductors from juxtaposed faces of adjacent electrodes being connected together. so that these faces'are at the same potentiahwhereby capacitance elfects between crystals are minimized.

All of the crystal blocks may be connected in parallel electrically, as by the conductors IL-the blocks being oriented, of course, so that all the crystals respond in the same manner to either compressional waves incident thereon or poten-' tials impressed between the electrodes l5, so that the output of the blocks is cumulative.

Adjacent crystal blocks are insulatinglyspaced 1. e,,'f. itii s jequallysensitive in all: dir .gtionsfnormal tofjthis a IIt will be lwappreciated that the crystal array is iacilely constructable "and can be fabricated" rectum-as dru ed l nit for mounting in' the housing1l0. 'Inasmuchas the guide 'posts-lim'erely n; engage the crystal blocks and the several crystals. 1

' areinterconnected'mechanically only by the sepfrom each other by separators l8, such as mm strips orblocks of ceramic having a low dielectric is highly directional in the direction 01 its length;

that is, the array is highly sensitive to waves in-,

'cidentf thereon normal 1 to its 'length and is but poorlysens'itive to waves incident thereon at angles to. this normaL'LvThis "directivity, which ob- 1 talus, 01' course, forfboth propagation andrecepytiomfis enhanced"'by gmalrin'g the end crystal j blocksdoubl the thickness of the intermediate -'blocks. w 1 a a I giltwill be 'notedthat heir-,rystal array provides I v surfaces exposedlto thefwav conveying medium ior all directions oipropagation'or reception-oi are employed, three groups of crystals at an angle of 60 degrees to one another may be utilized. Other modifications may be made without departing from the scope and spirit of the invention v as defined by the appended claims.

What is claimed is:

'- 1. A compressional wavetranslating device comprising a plurality "oi! rectangular, longitudiwave energy; The groups oi crystals, because of --their arrangement and symmetry with respect'to the arl'ay it is lessentially non directional an arat'o rs |8,Ithe mechanicalrestraint to vibration mechanical forces" impressed thereupon is small and is, localized in the region ofthe stress orJvibrational antinodes of the crystal blocks. Hence, high sensitivity and translating emciency-are' realized. I In the device illustrated in Fig. 4, the cry blocks M are constructed, arranged and connec ed mechanically and electrically-in the sam manner as inthe device shown in Figs. 1'to3l3 the longitudinal axis of the array provide a subwstantialiy circular propagation and reception pat.- 5, v tern concentric with this axis so that although, s in ied her i o e'. the 'array is' sharply im V 1y tive in the direction of the. longitudinal 01s" ithereoli V plurality ofrectangul nallywibratile,piezoelectric crystal blocks arrayed in spaced superposed relation with adjacentblocks'extending at right angles to each other, insulating spacer :means between adjacent 5 blocks,-and substantially parallel, laterally. spaced insulatingfguiderpostsextending longitudinally of V oigsaid ibloclrs ito maintain the angular relation the'array otblocks and slidably engaging the sides .12. :Aj compressional wavetranslating device 'comprising an insulating support structure in- =.cl uding-an endvmemberand four parallel guide extending from said end'member and arranged at"thecorners:of a square, two groups oi! piezoelectric; crystal blocks arrayed rnately' positioned, and uplin'g adjacent blocks to V M v centers thereof.

1 3'. asubmarme signs, rig device comprising a piezoelectric crystal blocks ot the same length 'arrayedinv superposed,

. or thecrystalsin response to either electricalor centrally" aligned relation with alternate crystal blocks extending 'at'right angles to the other blocks, the-length of said blocks being substantlallyone-halt wave-length of a predetermined jacent blocks at the c'enter'portions' thereof, po-

However, each blockis provided with'a central aperture in which an insulating guide or positioning member 20 is fitted, and only two guide posts l3 are provided. These posts 13 may be omitted, if desired, and the leading-in conductors I6 brought out to conductors I! located "in.

the positions of the posts l3 shown in Fig.4.

device will be dependent upon the compressional wave energy transmission characteristics of the housing Ill. Ina particularly advantageous construction, the housing may be fabricated of an expanded metal frame having a covering of thin sheet" steel, as described in my Patent'2,41'7,829, granted March 25, 1947,,which is characterized by high transparency to supersonic compressional wave energy and substantially no variation of transmission characteristic with angle of incidence of the waves thereon. Other materials may be employed for the housing, such as a cellulose acetone butyrate plastic known commercially as Tenite II" and a laminated molded wood impregnated with a phenolic condensation product known commercially as Impreg.

Although specific embodiments of this invention have been illustrated and described, it will be understood that they are but illustrative and that various modifications may be made therein. For example, although in the device described hereinabove, two groups of crystals in quadrature 'sitioning'means' laterally adjacent and engaging said blocks, 7 and means electrically connecting said 'blocks 'in parallel, saidcouplingmeans constituting the onlyvibration restraining mechanical interconnection Tbetween'said blocks.

4. A compressional wave translating device comprisingiaghousing transparent to compressional wave-energy, an array of longitudinally vlbratile, rectangular, piezoelectric crystal blocks mounted in spaced superposed relation within The sensitivity and directional pattern oi the said housing and spaced from the inner wall thereof, all ot'said blocks being of a length substantially' equal to one half wavelength of a pre-' assigned frequency and adjacent blocks extending at right angles to one another, and means for mechanically interconnecting said blocks solely adjacent the centers thereof.

ARTHUR C. KELLER.

' REFERENCES crrsn The following references are of record in the die of this patent:

Great Britain Feb. 21, 1930 relation above said end member, 7 

